Drawworks and motor

ABSTRACT

A rig system with a drawworks motor and a drawworks motor useful in systems for wellbore operations, the system in certain aspects including a rig, a derrick on the rig, a drawworks, the drawworks motor for powering the drawworks, the motor including a motor shaft, a plurality of power cables for providing electrical power to the motor, a portion of each of the plurality of power cables passing through the shaft, and a plurality of channels passing through the shaft adjacent the power cables and spaced-apart therefrom, the channels for the passage therethrough of a heat exchange fluid for the exchange of heat with the power cables to maintain the power cables at a desired temperature.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to: drawworks, particularly to drawworks used with well drilling rigs in the performance of various operations on the rig; motors for such drawworks; power cables for such motors; and methods of using these things.

2. Description of Related Art

A drawworks is used in connection the raising and lowering of a variety of loads. In wellbore operations, such as drilling a well for oil or gas, a drawworks is used on a rig or with a derrick to hold and to raise and lower tubulars, e.g., but not limited to, a drill string and associated equipment above, into and/or out of a wellbore. A traveling block, having an appropriate hook or other similar assembly typically used for the raising and lowering operations is secured in block-and-tackle fashion to a crown block or other limit fixture located at the top of the rig or derrick. Operation of the traveling block is performed by means of a hoist cable or line, one end of which is secured to the rig floor or ground forming a “dead line”, with the other end secured to the drawworks proper and forming a “fast line”. Other load bearing assemblies are possible. Herein such load bearing assemblies are referred to as the “traveling block”, which can include a hook or other attachment, associated equipment, and/or other load associated therewith as it moves up and down.

In certain aspects, prior drawworks include a rotatable cylindrical drum upon which cable or fast line is wound by means of a prime mover (motor) and power assembly. The drawworks and traveling block assembly are automatically controlled or operated by an operator, e.g. a “driller”. In association with the raising of the traveling block, the prime mover (motor) is controlled by the operator e.g. with a foot or hand throttle; or the drawworks is automatically controlled by a suitable control system. The drawworks is supplied with one or more suitable brakes—for routine operation and for emergencies. The lines or wirelines are usually wire ropes or steel cables, although other materials have also been used.

Drawworks' motors are relatively heavy high-horsepower motors. They provide the power to raise and lower loads that can be many hundred ton loads, some exceeding a thousand tons. Power cables that provide power to these motors can heat up due to the high flow of current through the cables. In the past these cables have been insulated and cooled with air flow or cooled by the media in which a cable is located, e.g. the earth. With certain known cooling methods there is insufficient heat exchange and, regarding certain cooling media, the media must be compatible with cable insulation or with the cable wires.

There is a need, recognized by the present inventors, for effective and efficient drawworks systems and motors for them. There is a need, recognized by the present inventors, for effective and efficient drawworks motor.

There is a need, recognized by the present inventors, for an effective and efficient drawworks motor with power cables maintained at an efficient operating temperature.

BRIEF SUMMARY OF THE INVENTION

The present invention, in certain embodiments, provides a drawworks system with a motor having cooled power cables. In one aspect the power cables are cooled by heat exchange with cooling flowing adjacent the power cables. In one aspect, the power cables are encased in insulating material to further maintain them at a desired operating temperature. The heat exchange fluid can be any suitable fluid, e.g., but not limited to water, freon, liquid nitrogen, or antifreeze.

The present invention discloses, in certain aspects, systems for use in wellbore operations, the systems including: a rig; a derrick on the rig; a drawworks; a motor for powering the drawworks, the motor having a motor shaft, a plurality of power cables for providing electrical power to the motor, a portion of each of the plurality of power cables passing through the shaft; and a plurality of channels passing through the shaft adjacent the power cables and spaced-apart therefrom, the channels for the passage therethrough of a heat exchange fluid for the exchange of heat with the power cables to cool the power cables.

The present invention discloses, in certain aspects, motors having: a motor shaft; a plurality of power cables for providing electrical power to the motor; a portion of each of the plurality of power cables passing through the shaft; and a plurality of channels passing through the shaft adjacent the power cables and spaced-apart therefrom, the channels for the passage therethrough of a heat exchange fluid for the exchange of heat with the power cables to cool the power cables.

The present invention discloses, in certain aspects, methods for moving an item in a rig system, the rig system for use in wellbore operations, the rig system as any described herein; the method including: raising or lowering the item by running a rig motor; and cooling motor power cables by passing heat exchange fluid through a plurality of channels adjacent the cables.

The present invention discloses, in certain aspects, motors including: a motor shaft; at least one power cable for providing electrical power to the motor; a portion of the at least one power cable passing through the shaft; and at least one channel passing through the shaft adjacent the at least one power cable and spaced-apart therefrom, the at least one channel for the passage therethrough of a heat exchange fluid for the exchange of heat with the at least one power cable to cool the at least one power cable.

Accordingly, the present invention includes features and advantages which are believed to enable it to advance drawworks and drawworks motor technology. Characteristics and advantages of the present invention described above and additional features and benefits will be readily apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments and referring to the accompanying drawings.

What follows are some of, but not all, the objects of this invention. In addition to the specific objects stated below for at least certain preferred embodiments of the invention, there are other objects and purposes which will be readily apparent to one of skill in this art who has the benefit of this invention's teachings and disclosures. It is, therefore, an object of at least certain preferred embodiments of the present invention to provide: new, useful, unique, efficient, nonobvious systems and methods for drawworks, drawworks motors, power cables for such motors, and cooling of such cables.

Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures, functions, and/or results achieved. Features of the invention have been broadly described so that the detailed descriptions that follow may be better understood, and in order that the contributions of this invention to the arts may be better appreciated. There are, of course, additional aspects of the invention described below and which may be included in the subject matter of the claims to this invention. Those skilled in the art who have the benefit of this invention, its teachings, and suggestions will appreciate that the conceptions of this disclosure may be used as a creative basis for designing other structures, methods and systems for carrying out and practicing the present invention. The claims of this invention are to be read to include any legally equivalent devices or methods which do not depart from the spirit and scope of the present invention.

The present invention recognizes and addresses the problems and needs in this area and provides a solution to those problems and a satisfactory meeting of those needs in its various possible embodiments and equivalents thereof. To one of skill in this art who has the benefits of this invention's realizations, teachings, disclosures, and suggestions, other purposes and advantages will be appreciated from the following description of certain preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings. The detail in these descriptions is not intended to thwart this patent's object to claim this invention no matter how others may later attempt to disguise it by variations in form, changes, or additions of further improvements.

The Abstract that is part hereof is to enable the U.S. Patent and Trademark Office and the public generally, and scientists, engineers, researchers, and practitioners in the art who are not familiar with patent terms or legal terms of phraseology to determine quickly from a cursory inspection or review the nature and general area of the disclosure of this invention. The Abstract is neither intended to define the invention, which is done by the claims, nor is it intended to be limiting of the scope of the invention or of the claims in any way.

It will be understood that the various embodiments of the present invention may include one, some, or all of the disclosed, described, and/or enumerated improvements and/or technical advantages and/or elements in claims to this invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A more particular description of embodiments of the invention briefly summarized above may be had by references to the embodiments which are shown in the drawings which form a part of this specification. These drawings illustrate certain preferred embodiments and are not to be used to improperly limit the scope of the invention which may have other equally effective or equivalent embodiments.

FIG. 1 is a schematic view of a system according to the present invention.

FIG. 1A is a schematic view of a motor of the system of FIG. 1.

FIG. 2A is a side cross-section view of a drawworks according to the present invention.

FIG. 2B is an enlarged perspective view of a motor of the drawworks of FIG. 2A.

FIG. 2C is an end view of part of the motor of FIG. 2A.

FIG. 3A is a perspective view of a shaft of the motor of FIG. 2A.

FIG. 3B is a perspective view of part of the shaft of FIG. 3A.

FIG. 3C is an end view of part of the shaft of FIG. 3A.

FIG. 4A is a perspective view of a shaft according to the present invention for a motor according to the present invention.

FIG. 4B is an end view of the shaft of FIG. 4A.

Presently preferred embodiments of the invention are shown in the above-identified figures and described in detail below. It should be understood that the appended drawings and description herein are of preferred embodiments and are not intended to limit the invention or the appended claims. On the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims. In showing and describing the preferred embodiments, like or identical reference numerals are used to identify common or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness.

As used herein and throughout all the various portions (and headings) of this patent, the terms “invention”, “present invention” and variations thereof mean one or more embodiment, and are not intended to mean the claimed invention of any particular appended claim(s) or all of the appended claims. Accordingly, the subject or topic of each such reference is not automatically or necessarily part of, or required by, any particular claim(s) merely because of such reference.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1 and FIG. 1A, drilling system 10 according to the present invention is used in conjunction with a drilling rig R according to the present invention. The drilling rig R has a derrick 10 with a crown block 15. Suspended by a rope arrangement 17 from the crown block 15 is a traveling block 20, or load bearing part, for supporting a hook structure 25. Alternatively, the traveling block 20 can be formed as a hook block or other conventional related load bearing parts of a hoist assembly attached to the rope arrangement 17. As used herein, the term “hook block” refers to the load bearing part 20 of the hoist assembly.

A hoisting line 30 is securely fixed at one end to ground by a dead line 35 and a dead line anchor 40. The other end of the hoisting line 30 forms a fast line 45 attached to a drawworks 50 according to the present invention. The drawworks 50 includes one, two (or more) or more electrical motors 55 according to the present invention for rotating a cylindrical rotatable drum 65 for wrapping and unwrapping the fast line 45 as required for operation of the associated crown block 15 and traveling block 20. The rotatable drum 65 is also referred to as a winding drum or a hoisting drum. A brake arrangement 70 connected to the drawworks 50 typically includes a band type primary brake or disk brake, an auxiliary brake, such as an eddy current type brake or a magnetic brake, and an emergency brake. Various sensors 90 and 92 provide information to a drawworks control system 80. Electrical power from a power source 60 (e.g. a typical rig power apparatus) is provided to cables 62 according to the present invention via a junction box 64. Coolant channels 66 adjacent the cables 62 provide for indirect heat exchange cooling of the cables 62. Channels 68, in fluid communication with the channels 66, provide for the exit of fluid pumped through the channels 66 by a pump 72 from a fluid reservoir 74.

FIGS. 2A-2C show a drawworks 100 according to the present invention which includes a rotatable drum 110 rotatably secured to mounts 102, 104 on a base 106. A rotor 132 of a motor 130 encompasses a stator 134. The stator 134 has a body 131 with a plurality of windings 136 on a body 135 and the rotor 132 has a plurality of permanent magnets 138. A shaft 140 projects from the body 131 through the drum 110 and through one of the mounts 102. The motor is interconnected with a gear system 105.

Power cables 150 (or a cable) extend from outside the drum 110 (e.g. from a junction box), through a channel or central bore 142 in the shaft 140, and to connections with the stator windings 136, exiting through a hole 144 in the shaft 140 for connection to the windings 136. The present invention includes within its scope a motor with at least one power cable. The shaft 140 has one or a plurality of fluid channels 146 (multiple channels shown) through which heat exchange fluid is pumped. In communication with these shaft channels 146 are a plurality of corresponding channels 139 in the body 131 of the stator 134. The fluid pumped through the channels 146 is conveyed, via the channels 139 away from the stator 134. Alternatively, certain of the channels 146 are input channels and certain of the channels 146 are output channels, with a pump pumping the heat exchange fluid into the input channels and out the output channels (at the same end of the shaft; the right end as viewed in FIG. 2A). optionally, the power cables may run through any part of the shaft (other than the central bore); and the water channels, shown surrounding the power cables, may optionally, be centrally located or located as desired.

An inner housing 160 with ends 162, 164 contains the stator 134. These ends 162, 164 move on bearings 166, 168 respectively. The shaft 140 is on the bearings 114 in a drum end 116 and on bearings 172 in the mount 102.

Each cable 150 includes a plurality of wires 154 (e.g. copper or aluminum) running therethrough potted in a potting material 154. For three phase power transmission, these wires are in groups of three.

FIGS. 4A and 4B illustrate an end 181 of a shaft 180 (like the shaft 140) which is part of or connected to a body (not shown; like the body 131). The shaft 180 has a plurality of fluid channels 186 therethrough (like the channels 146) and a central channel 182 (like the channel 142). A plurality of cables 190 (like the cables 150) run through the shaft 180.

A heat exchange fluid 188 (e.g. water, antifreeze, oil, or mineral oil) is pumped through the channels 186. The cables 190 include a plurality of conducting wires 192 (like the wires 154) are insulated with an insulating jacket 196, e.g. of silicon or high temperature silicones. In one aspect the wires 192 are in group of three bundled together and twisted along their length to minimize inductance heating of metal and objects adjacent the cables. In one aspect each wire has individual insulation. In one aspect each grouping of three wires constitutes a power cable.

The cables are all potted in a matrix 198 of potting material (e.g., but not limited to, e.g. insulating material with a high dielectric constant such as cable jacketing material made from, e.g. insulating resin compounds, thermosetting epoxy material). A junction box used with such cables, e.g. the junction box 64, FIG. 1A is, optionally sealed to prevent water leakage.

By using the channels adjacent the power cables to flow heat exchange fluid for cooling the power cables, the overall size of the power cables is reduced as compared to certain prior art power cables, e.g. from ⅓ to ⅔ size reduction, and, in certain cases, a 50% reduction in size. In certain aspects less of the conductor metal (copper or aluminum) is needed to transmit a desired amount of power. For example, in certain aspects with four cables, each conducting 800 amps (total 3600 amps) with basic parameters (geometry, size, material conductivity of cable insulation, number of cables) being equal, a system according to the present invention with water cooling will be about fifty percent smaller in size than a comparable prior art system with air cooling.

As shown e.g. in FIG. 2A the rotor and stator are housed within a drum or housing. It is within the scope of the present invention to provide a motor according to the present invention which is outside such a drum or housing. It is within the scope of the present invention to provide cooling of power cables according to the present invention, cooled power cables according to the present invention, and a motor with such cables according to the present invention, in one aspect with the motor outside a drum or housing for a drawworks or other apparatus.

The present invention, therefore, provides, in at least certain but not necessarily all embodiments, a system for use in wellbore operations, the system including: a rig; a derrick on the rig; a drawworks; a motor for powering the drawworks, the motor including a motor shaft, a plurality of power cables for providing electrical power to the motor, a portion of each of the plurality of power cables passing through the shaft and a plurality of channels passing through the shaft adjacent the power cables and spaced-apart therefrom, the channels for the passage therethrough of a heat exchange fluid for the exchange of heat with the power cables to cool the power cables. Such an apparatus may have one or some, in any possible combination, of the following: a drum on the drawworks for taking in and playing out a line, and the motor disposed within and connected to the drum; the power cables including at least one wire through which electric current flows, the wires insulated with insulating material; each power cable comprises a plurality of conducting wires, each conducting wire is insulated, and all the power cables are potted in a matrix of potting material; the power cables extend within the motor shaft along a first length, the channels for the passage therethrough of a heat exchange fluid extend within the motor shaft along a second length, and the second length at least as long as the first length; the motor shaft having a center bore, the power cables extend through the center bore of the motor shaft, and the channels are around the center bore; and/or the motor shaft having a first portion, a second portion, and a stator between the first portion and the second portion, the channels extending from the first portion, through the stator, and to the second portion, and the heat exchange fluid entering the channels at the first portion and exiting from the second portion.

The present invention, therefore, provides, in at least certain but not necessarily all embodiments, a system for use in wellbore operations, the system including: a rig; a derrick on the rig; a drawworks; a motor for powering the drawworks, the motor including a motor shaft, a plurality of power cables for providing electrical power to the motor, a portion of each of the plurality of power cables passing through the shaft, a plurality of channels passing through the shaft adjacent the power cables and spaced-apart therefrom, the channels for the passage therethrough of a heat exchange fluid for the exchange of heat with the power cables to cool the power cables, a drum on the drawworks for taking in and playing out a line, the motor disposed within and connected to the drum, and wherein motor shaft has a center bore, the power cables extend through the center bore of the motor shaft, and the channels are around the center bore.

The present invention, therefore, provides, in at least certain but not necessarily all embodiments, a system for use in wellbore operations, the system including: a rig; a derrick on the rig; a drawworks; a motor for powering the drawworks, the motor including a motor shaft, a plurality of power cables for providing electrical power to the motor, a portion of each of the plurality of power cables passing through the shaft, a plurality of channels passing through the shaft adjacent the power cables and spaced-apart therefrom, the channels for the passage therethrough of a heat exchange fluid for the exchange of heat with the power cables to cool the power cables, a drum on the drawworks for taking in and playing out a line, the motor disposed within and connected to the drum, and wherein motor shaft has a center bore, the power cables extend through the center bore of the motor shaft, and the channels are around the center bore.

The present invention, therefore, provides, in at least certain but not necessarily all embodiments, a motor including: a motor shaft; a plurality of power cables for providing electrical power to the motor; a portion of each of the plurality of power cables passing through the shaft; and a plurality of channels passing through the shaft adjacent the power cables and spaced-apart therefrom, the channels for the passage therethrough of a heat exchange fluid for the exchange of heat with the power cables to cool the power cables. Such an apparatus may have one or some, in any possible combination, of the following: a drum for taking in and playing out a line, and the motor disposed within and connected to the drum; the power cables including at least one wire through which electric current flows, the wires insulated with insulating material; each power cable is a plurality of conducting wires, each conducting wire is insulated, and all the power cables are potted in a matrix of potting material; the power cables extending within the motor shaft along a first length, the channels for the passage therethrough of a heat exchange fluid extend within the motor shaft along a second length, and the second length at least as long as the first length; the motor shaft having a center bore, the power cables extending through the center bore of the motor shaft, and the channels are around the center bore; and/or the motor shaft having a first portion, a second portion, and a stator between the first portion and the second portion, the channels extending from the first portion, through the stator, and to the second portion, and the heat exchange fluid entering the channels at the first portion and exiting from the second portion.

The present invention, therefore, provides, in at least certain but not necessarily all embodiments, a method for moving an item in a rig system, the rig system for use in wellbore operations, the rig system being any rig disclosed herein, the method including: raising or lowering the item by running a rig motor, and cooling a power cable or power cables of the rig motor by passing heat exchange fluid through a plurality of channels adjacent the cable or cables. Such an apparatus may have one or some, in any possible combination, of the following: the power cable or cables extend within a motor shaft along a first length, the channels for the passage therethrough of a heat exchange fluid extend within the motor shaft along a second length, and the second length at least as long as the first length; and/or the motor shaft has a center bore, the power cables extend through the center bore of the motor shaft, and the channels are around the center bore.

The present invention, therefore, provides, in at least certain but not necessarily all embodiments, a motor including: a motor shaft; at least one power cable for providing electrical power to the motor; a portion of the at least one power cable passing through the shaft; and at least one channel passing through the shaft adjacent the at least one power cable and spaced-apart therefrom, the at least one channel for the passage therethrough of a heat exchange fluid for the exchange of heat with the at least one power cable to cool the at least one power cable.

In conclusion, therefore, it is seen that the present invention and the embodiments disclosed herein and those covered by the appended claims are well adapted to carry out the objectives and obtain the ends set forth. Certain changes can be made in the subject matter without departing from the spirit and the scope of this invention. It is realized that changes are possible within the scope of this invention and it is further intended that each element or step recited in any of the following claims is to be understood as referring to all equivalent elements or steps. The following claims are intended to cover the invention as broadly as legally possible in whatever form it may be utilized. The invention claimed herein is new and novel in accordance with 35 U.S.C. § 102 and satisfies the conditions for patentability in § 102. The invention claimed herein is not obvious in accordance with 35 U.S.C. § 103 and satisfies the conditions for patentability in § 103. This specification and the claims that follow are in accordance with all of the requirements of 35 U.S.C. § 112. The inventor may rely on the Doctrine of Equivalents to determine and assess the scope of their invention and of the claims that follow as they may pertain to apparatus not materially departing from, but outside of, the literal scope of the invention as set forth in the following claims. Any patent or patent application referred to herein buy patent number or application number is incorporated fully herein for all purposes. 

1. A system for use in wellbore operations, the system comprising a rig, a derrick on the rig, a drawworks, a motor for powering the drawworks, the motor comprising a motor shaft, a plurality of power cables for providing electrical power to the motor, a portion of each of the plurality of power cables passing through the shaft, and a plurality of channels passing through the shaft adjacent the power cables and spaced-apart therefrom, the channels for the passage therethrough of a heat exchange fluid for the exchange of heat with the power cables to cool the power cables.
 2. The system of claim 1 further comprising a drum on the drawworks for taking in and playing out a line, and the motor disposed within and connected to the drum.
 3. The system of claim 1 further comprising the power cables including at least one wire through which electric current flows, the wires insulated with insulating material.
 4. The system of claim 3 wherein each power cable comprises a plurality of conducting wires, each conducting wire is insulated, and all the power cables are potted in a matrix of potting material.
 5. The system of claim 1 wherein the power cables extend within the motor shaft along a first length, the channels for the passage therethrough of a heat exchange fluid extend within the motor shaft along a second length, and the second length at least as long as the first length.
 6. The system of claim 1 wherein the motor shaft has a center bore, the power cables extend through the center bore of the motor shaft, and the channels are around the center bore.
 7. The system of claim 1 wherein the motor shaft has a first portion, a second portion, and a stator between the first portion and the second portion, the channels extend from the first portion, through the stator, and to the second portion, and the heat exchange fluid entering the channels at the first portion and exiting from the second portion.
 8. A system for use in wellbore operations, the system comprising a rig, a derrick on the rig, a drawworks, a motor for powering the drawworks, the motor comprising a motor shaft, a plurality of power cables for providing electrical power to the motor, a portion of each of the plurality of power cables passing through the shaft, a plurality of channels passing through the shaft adjacent the power cables and spaced-apart therefrom, the channels for the passage therethrough of a heat exchange fluid for the exchange of heat with the power cables to cool the power cables, a drum on the drawworks for taking in and playing out a line, the motor disposed within and connected to the drum, and wherein motor shaft has a center bore, the power cables extend through the center bore of the motor shaft, and the channels are around the center bore.
 9. A system for use in wellbore operations, the system comprising a rig, a derrick on the rig, a drawworks, a motor for powering the drawworks, the motor comprising a motor shaft, a plurality of power cables for providing electrical power to the motor, a portion of each of the plurality of power cables passing through the shaft, a plurality of channels passing through the shaft adjacent the power cables and spaced-apart therefrom, the channels for the passage therethrough of a heat exchange fluid for the exchange of heat with the power cables to cool the power cables, a drum on the drawworks for taking in and playing out a line, the motor disposed within and connected to the drum, and wherein motor shaft has a center bore, the power cables extend through the center bore of the motor shaft, and the channels are around the center bore.
 10. A motor comprising a motor shaft, a plurality of power cables for providing electrical power to the motor, a portion of each of the plurality of power cables passing through the shaft, and a plurality of channels passing through the shaft adjacent the power cables and spaced-apart therefrom, the channels for the passage therethrough of a heat exchange fluid for the exchange of heat with the power cables to cool the power cables.
 11. The motor of claim 10 further comprising a drum for taking in and playing out a line, and the motor disposed within and connected to the drum.
 12. The motor of claim 10 further comprising the power cables including at least one wire through which electric current flows, the wires insulated with insulating material.
 13. The motor of claim 12 wherein each power cable comprises a plurality of conducting wires, each conducting wire is insulated, and all the power cables are potted in a matrix of potting material.
 14. The motor of claim 10 wherein the power cables extend within the motor shaft along a first length, the channels for the passage therethrough of a heat exchange fluid extend within the motor shaft along a second length, and the second length at least as long as the first length.
 15. The motor of claim 10 wherein the motor shaft has a center bore, the power cables extend through the center bore of the motor shaft, and the channels are around the center bore.
 16. The motor of claim 10 wherein the motor shaft has a first portion, a second portion, and a stator between the first portion and the second portion, the channels extend from the first portion, through the stator, and to the second portion, and the heat exchange fluid entering the channels at the first portion and exiting from the second portion.
 17. A method for moving an item in a rig system, the rig system for use in wellbore operations, the rig system comprising a rig, a derrick on the rig, an item suspended on a line in the derrick, a drawworks for moving the line, a motor for powering the drawworks, the motor comprising a motor shaft, a plurality of power cables for providing electrical power to the motor, a portion of each of the plurality of power cables passing through the shaft, and a plurality of channels passing through the shaft adjacent the power cables and spaced-apart therefrom, the channels for the passage therethrough of a heat exchange fluid for the exchange of heat with the power cables to cool the power cables, the method comprising raising or lowering the item by running the motor, and cooling the power cables by passing the heat exchange fluid through the plurality of channels.
 18. The method of claim 17 wherein the power cables extend within the motor shaft along a first length, the channels for the passage therethrough of a heat exchange fluid extend within the motor shaft along a second length, and the second length at least as long as the first length.
 19. The method of claim 17 wherein the motor shaft has a center bore, the power cables extend through the center bore of the motor shaft, and the channels are around the center bore.
 20. A motor comprising a motor shaft, at least one power cable for providing electrical power to the motor, a portion of each of the at least one power cable passing through the shaft, and at least one channel passing through the shaft adjacent the at least one power cable and spaced-apart therefrom, the at least one channel for the passage therethrough of a heat exchange fluid for the exchange of heat with the at least one power cable to cool the at least one power cable. 